# CVE-2021-47114: ocfs2: fix data corruption by fallocate


- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 15 Mar 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47114, GHSA-9wr4-x5hv-2rw2, UBUNTU-CVE-2021-47114

## What is CVE-2021-47114?

CVE-2021-47114 is a medium-severity vulnerability in Linux kernel, published on 15 Mar 2024. 

### Official description

In the Linux kernel, the following vulnerability has been resolved:

ocfs2: fix data corruption by fallocate

When fallocate punches holes out of inode size, if original isize is in
the middle of last cluster, then the part from isize to the end of the
cluster will be zeroed with buffer write, at that time isize is not yet
updated to match the new size, if writeback is kicked in, it will invoke
ocfs2_writepage()->block_write_full_page() where the pages out of inode
size will be dropped.  That will cause file corruption.  Fix this by
zero out eof blocks when extending the inode size.

Running the following command with qemu-image 4.2.1 can get a corrupted
coverted image file easily.

    qemu-img convert -p -t none -T none -f qcow2 $qcow_image \
             -O qcow2 -o compat=1.1 $qcow_image.conv

The usage of fallocate in qemu is like this, it first punches holes out
of inode size, then extend the inode size.

    fallocate(11, FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE, 2276196352, 65536) = 0
    fallocate(11, 0, 2276196352, 65536) = 0

v1: https://www.spinics.net/lists/linux-fsdevel/msg193999.html
v2: https://lore.kernel.org/linux-fsdevel/20210525093034.GB4112@quack2.suse.cz/T/

## Which versions are affected by CVE-2021-47114?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47114?

Upgrade to a fixed version.

## Is CVE-2021-47114 being exploited?

There is no known exploitation of CVE-2021-47114 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-47114 and fix it if it is affected.

What it is: CVE-2021-47114 is a medium-severity vulnerability in Linux kernel, published on 15 Mar 2024. 
Exploitation: There is no known exploitation of CVE-2021-47114 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-47114/ (Markdown: https://insights.sbomify.com/CVE-2021-47114/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47114
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47114
- OSV: https://osv.dev/vulnerability/CVE-2021-47114

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47114/
Summaries are generated and may contain mistakes; the official description above is the record.